Project 56 -1955/56 Test: Project 56 No. 1 Time: 22:10 01/11/1955 GMT Location: NTS Area 11a Type: Surface Yield: Zero One-point safety test of an all-oralloy prototype sealed pit weapon that was similar to the Plumbbob Priscilla and Redwing Lacrosse devices (tested at 37 and 40 kt respectively), probably the primary for the TX-15/39 and W-27. To ensure safety of the deployed design, two changes were made to enhance the nuclear output of this test. More oralloy was used than would be present in the war-reserve model. Also 3 external neutron sources ("zippers") were used to ensure a large neutron population at the moment of criticality. The device was 94cm in diameter and weighed 272kg. Test: Project 56 No. 2 Time: 21:15 03/11/1955 GMT Location: NTS Area 11b Type: Surface Yield: Zero One-point safety test of the plutonium containing W-25 sealed pit weapon. The device was 44 cm in diameter, 67cm long, and weighed 99kg. 3 zippers were used as neutron sources. Test: Project 56 No. 3 Time: 19:55 05/11/1955 GMT Location: NTS Area 11c Type: Surface Yield: Zero This was a one-point safety test for the prototype TX/W-28 primary. The 43cm diameter nuclear system weighed 65kg, the total device weighed 125kg. 3 zippers were used as neutron sources. Test: Project 56 No. 4 Time: 21:30 18/01/1956 GMT Location: NTS Area 11d Type: Surface Yield: Slight (10-100 tons) Like shot No. 3 this was a one-point safety test for the prototype TX/W-28 primary. The device was basically identical except that 6 zippers were used as neutron sources. The enhanced yield (compared to No. 3) was probably due to the larger neutron population injected into the core. Due to the low rate of neutron multiplication possible in this slightly supercritical system, only a limited amount of neutron multiplication is possible while the core remains compressed. A larger initial neutron population results in a larger final neutron population (and thus total fission output).